I've found a janky workaround using ForceBindIP.

.\ForceBindIP64.exe 192.168.128.1 .\LibreWolf\librewolf.exe -profile Profiles\Default

This bypasses Librewolf Portable entirely, launching the browser executable itself and manually specifying the profile path so that we don't leave a trace in the AppData folder and actually make the data "portable". For this to actually work, you have to go in about:config and set browser.launcherProcess.enabled to false so that ForceBindIP actually binds.

Support for this could definitely be implemented within the Portable launcher, but I'm not putting my hopes up.

I know my school will sometimes use last year's CC versions because they're familiar with it, and it's been tested to work with what they want to teach, so it won't just break or not function as expected out of nowhere. Now why they use 2020's version in 2023 is beyond me, stuff generally does not change drastically in 3 years.

I speak Canadian French so we may have different definitions but even I have no clue how to translate this in a way that makes sense in English.

Literal translation would be "[you're] the fucked of your race" (I could precise details about "fucking" present in the French word, but I am not risking any more of my credibility for that.)